Increased usage of renewable energy sources such as solar radiation is important in reducing dependence upon foreign sources of oil and decreasing greenhouse gases. Devices have been developed in the past that track the motion of the Sun to re-direct and concentrate incident solar radiation. Prior art includes, for example, the use of a parabolic dish mirror with a central axis that is pointed generally toward the Sun. Incidental solar radiation is received and reflected by the parabolic dish mirror and concentrated at its focus, where a thermal target can be mounted so that it can be heated. Such a parabolic dish mirror has been supported for independent movement by a two-axis tracking support mounted atop a supporting structure such as a tower. In some instances, optical encoders associated with the tracking support provide signals indicative of the direction and amount of rotation of the parabolic dish mirror so that motor drives and a control system can be used to track the Sun and increase the efficiency of the energy transfer.
Similar existing devices utilize a parabolic trough mirror whose focal line aligns with the Sun. A tracking support carries the parabolic trough mirror, typically mounted atop a tower. Incident light rays from the Sun are collected and reflected by the parabolic trough mirror and concentrated on a pipe that extends along the focal line effecting a heat transfer to a fluid such as water or liquid sodium. The heating efficiency can be improved by targeting mechanisms that cause the parabolic trough mirror to pivot and track the Sun.
Another variation of the prior art utilizes a heliostat flat mirror that receives incident light rays from the Sun and reflects them against a thermal target atop a tower. The flat-mirror heliostat may be supported by a two-axis tracking device which may be elevated on a tower. Drive mechanisms may control the azimuth and elevation of the flat mirror to keep the Sun's rays focused on the target thermal collector.
Cost and complexity of design are frequently encountered disadvantages to the prior art devices in this field. Tracking frames are historically often cumbersome and require significant power to drive in tracking. Additionally, the need for individual tracking sensor units on mirror heliostats in order to keep them individually pointed can significantly add to the expense of the units.